Transcript

Thousands of dead fish have been washed up on the shores of Fiji and Vanuatu as El Niño causes high water temperatures.

It's the same warm water that is propelling Cyclone Winston in an unpredictable path around and through Tonga and Fiji for a second time this week.

Alex Perrottet reports.

Victor Bonito is a scientist and the Director of Reef Explorer Fiji. He says the sight of thousands of dead fish around the country's coral coast - the south coast of Fiji's main island Viti Levu - was hard to take in.

VICTOR BONITO: It's quite an uncommon event I should say and very sad to see all these fish dead and washed up on the shore and at the surface struggling for air.

Victor Bonito says the hot water - around 34 to 36 degrees - killed off the fish, but also the all-important coral algae, meaning the coral was drained of colour - or bleached - in a matter of days.

VICTOR BONITO: It's going to impact the fishing ground for many years to come. Corals are the foundation species of the reef. Without corals we don't really have the habitat that supports the local fish communities that local people depend on. Obviously the reef in the areas affected won't be as attractive to tourism as well.

He says although he is not keen to see Cyclone Winston return to Fiji, it's a double-edged sword as the storm will bring cooler rains and cloud cover to help the coral reef recover. The Cyclone hit Fiji's southern Lau group earlier in the week and then hit Tonga, but is predicted to make a hairpin turn and hit more of Tonga and then Fiji in the next few days. A climate scientist at New Zealand's National Institute of Water and Atmospheric Research, or NIWA, Nava Fedaeff, says El Niño means the warm waters provide plenty of scope for cyclones to change track.

NAVA FEDAEFF: Well one of the reasons why is just because of El Niño, there are larger area of warmer than normal sea surface temperatures in the Pacific and you need to have warm water, at least 26.5 degrees, to have tropical cyclones. And when you've got a bigger pool, they've just got more places to go.

Nava Fedaeff says New Zealand also needs to be wary of rains, winds and high swells as a result of the cyclone's movements. Hundreds of fish were also washed ashore in Vanuatu in the past few days, and Rocky Kaku, from the Fisheries Department says people on the island of Efate are worried about their livelihoods.

ROCKY KAKU: They are quite worried about the fish, which some of them benefit for their livelihood, they use the fish for food and so since we are in the hot season they are quite worried about what they will eat and what they will make money out of in the coming months or future.

The Pacific Community's Brad Moore says countries are slowly bringing in bans on selling fish from night time fishing, which hits vulnerable fish stocks and further damages the reefs.

BRAD MOORE: People are night diving with spears, fishing with other destructive methods and the main targets of these fisheries are really the herbivores while they're asleep which is basically akin to shooting fish in a barrel. And we've seen that in locations where herbivores have been protected, so inside marine protected areas, for example, they've cleaned up the reef and the coral have managed to come back.

Brad Moore and Victor Bonito say the herbivore fish are crucial to bringing the reefs back as soon as possible, but there's decades of damage already done.